Abstract
We propose a nonvolatile terahertz (THz) switch which is able to perform the switching with transient stimulus. The device utilizes graphene as its floating-gate layer, which changes the transmissivity of THz signal by trapping the tunneling charges. The conventional top-down electrode configuration is replaced by a left-right electrode configuration, so THz signals could transmit through this device with the transmissivity being controlled by voltage pulses. The two electrodes are made of metals with different work functions. The resultant asymmetrical energy band structure ensures that both electrical programming and erasing are viable. With the aid of localized surface plasmon resonances in graphene ribbon arrays, the modulation depth is 89% provided that the Femi level of graphene is tuned between 0 and 0.2 eV by proper voltage pulses.
Highlights
The terahertz technology has gained increased research attention due to its industrial and academic applications[1,2]
Monolayer graphene vertically stacking on a 300-nm-thick SiO2 layer works as the floating-gate layer
It should be noted that the width of this transmission window for THz beams is on the scale of centimeters in practical devices
Summary
The terahertz technology has gained increased research attention due to its industrial and academic applications[1,2]. The floating-gate (FG) shown in Fig. 1(a) is so far the most successful configuration for the flash memory It relies on charges stored in the FG layer to tune the threshold voltage of the transistor. We note that active graphene layers in many of these modulators can be readily replaced by the graphene-based floating-gate in Fig. 1(b) with the two asymmetrical electrodes locating at the two sides of the waveguides. Since waveguide modes are confined to propagate along the graphene plane, the interaction length between THz/optical waves and graphene is extended, and Performance metrics in terms of power consumption, footprint, and modulation depth can be improved significantly for nonvolatile switching
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